Enantioselective hydrogenation of α-ketoesters over Pt/alumina modified with cinchonidine: theoretical investigation of the substrate-modifier interaction

摘要: Enantio-differentiation in the asymmetric hydrogenation of α-ketoesters to α-hydroxyesters over platinum catalysts modified with cinchona-alkaloid modifiers occurs through interaction ketoester cinchona modifier. The structure probable transition complex has been calculated for system methyl pyruvate (substrate) cinchonidine (modifier) using molecular mechanics and quantum chemistry techniques at both ab initio semiempirical levels. calculations suggest that protonated is energetically more likely interact substrate crucial via hydrogen bonding quinuclidine nitrogen oxygen α-carbonyl moiety pyruvate. In this transformed into a half-hydrogenated species which adsorbed on surface yields product methyll actate. Theoretical studies indicate adsorption leading (R) -methyl lactate favourable than corresponding (S) lactate, may be key enantio-differentiation.